This invention relates to a socket for a baseless lamp.
The baseless lamp, which is also referred to as a wedge base lamp, usually has a bulb with a sealed section formed at one end and a pair of leads folded along, and secured to, the outer surface of the sealed section and connected to a filament inside the bulb.
A socket, into which such a baseless lamp is inserted, has a cylindrical socket body made of a synthetic resin. The socket body has a bulb insertion cavity, into which the sealed section of the bulb is inserted, a flange formed on the outer periphery and clamp sections facing the flange. A mounting base, in which the socket is mounted, is clamped between the clamp sections and flange. A pair of contact members are inserted in the bulb insertion cavity. Each contact member has a pair of elastic contact portions which clamp the seal section of the bulb and are in elastic contact with the leads extending along the sealed section. Each contact member has a power supply terminal extending up to the top of the flange and in contact with a printed wiring formed on the mounting base.
The socket is inserted through a mounting hole formed in the mounting base and then turned in one direction. As a result, the mounting base is clamped between the clamp sections and the flange, whereby the socket body is mounted in the mounting base with the power supply terminals brought into contact with the printed wiring on the mounting base to form a power supply circuit.
In order to maintain a satisfactory contact between the end portion of the power supply terminal and printed wiring, an end portion of the power supply terminal is provided with a contact protuberance. The contact protuberance has a semispherical shape, so that it is brought into point contact with the printed wiring when it is urged thereagainst. The pressure of contact between the contact protuberance and printed wiring, therefore, is considerable. Thus, the printed wiring is liable to be damaged by the contact protuberance when the socket body inserted through the mounting hole of the mounting base is turned relative to the same.
Particularly, the printed wiring is formed from a copper foil printed on a polyester resin film. Therefore, with the rotation of the contact protuberance the copper foil is liable to be separated from the resin film, thus resulting in a contact failure.
Moreover, since the contact pressure between the protuberance and the printed wiring is relatively high, the operation of turning the socket requires a large force, thereby making the mounting of the socket troublesome.